In a medium skillet, heat the oil over medium heat. Add the onion and parsley, and cook, stirring occasionally, until the onion is transparent, about 3 minutes. Remove the skillet from the heat, transfer the mixture to a medium-size bowl, and allow it to cool.

Add the ham, bread crumbs, cheese, sour cream, egg, and a pinch of black pepper to the bowl, and mix well.

To assemble the turnovers: Place 2 heaping tablespoons of filling in the center of an empanada wrapper and lightly moisten the edge of the circle with the egg mixture. (If you use a pastry shell, you’ll first need to roll it out into a 5-inch circle on a lightly floured work surface.) Fold the pastry in half and press the edges firmly to seal. Crimp the edge with a fork dipped in flour and pierce the top with the fork to allow steam to escape. Repeat with the remaining wrappers and filling, then refrigerate the empanadas for 30 minutes or freeze for later use.

Make-Ahead Tip: To freeze your empanadas, place the unbaked turnovers in the freezer on a baking sheet lined with waxed paper. When frozen, stack them in sealable containers. Pop them in the oven frozen when you’re ready to bake them (following step 3). Just increase the baking time by 15 minutes.

Heat the oven to 375°. Brush the turnovers with the egg wash and bake them on a parchment-lined baking sheet on the upper oven rack until golden, about 20 to 25 minutes. Allow the empanadas to cool for a few minutes before serving. Makes 12 medium-size turnovers.